Mold and method for producing two-color injection-molded parts

ABSTRACT

A mold and a method for producing two-color injection-molded parts involves simultaneous injection of two kinds of molding material, in which a pressure difference between two kinds of molding materials is induced so that one of the molding materials is infiltrated into and bonded to the other molding material during solidification. The method for producing two-color injection-molded parts may include simultaneously injecting a first material and a second material to a first gate and a second gate to be filled in a first cavity and a second cavity, and closing the second gate such that the first molding material, which is not solidified, pushes a slide mold provided between a first mold block and a second mold block using a holing pressure of the first gate and is infiltrated into an unsolidified layer of the second molding material and solidified.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of and priority to KoreanPatent Application Number 10-2008-0068804 filed Jul. 15, 2008, theentire contents of which application is incorporated herein for allpurposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mold and a method for producingtwo-color injection-molded parts. More particularly, the presentinvention relates to a mold and a method for producing two-colorinjection-molded parts, in which a pressure difference between two kindsof molding materials, which are simultaneously injected, is induced sothat one of the molding materials is infiltrated into and bonded to theother molding material during solidification.

2. Description of Related Art

It is well known that an injection molding process is used tomanufacture plastic parts in the field of automotive industry. Ingeneral, the injection molding process uses plastic materials that havea single color to manufacture plastic parts having the correspondingcolor.

A component of a vehicle such as a door panel, for example, is generallyformed of a plastic material having a single color, which does not makea good impression on users. As an alternative plan, a door panelassembly is manufactured by assembling a plurality of parts having atleast one color.

However, such a method has problems in that the process of assemblingthe plurality of parts which constitute the door panel assembly is timeconsuming, and thus increases the manufacturing cost. In order to solvesuch problems, conventionally, molding materials having different colorsare used to produce two-color injection-molded parts.

FIG. 1 is a diagram schematically showing a conventional process forproducing two-color injection-molded parts.

As shown in FIG. 1, the conventional method for producing two-colorinjection-molded parts uses a mold including two cavities in whichmolding materials having different colors are filled. After a firstmolding material is firstly injected into a first cavity 1, a secondmold block 4 is moved back to open a second cavity 2, and then a secondmolding material is secondly injected into the second cavity 2. Aholding pressure is maintained until the injected molding materials aresolidified and a cooling step is performed such that the firstlyinjected molding material and the secondly injected molding material arebonded to each other, thus obtaining the two-color injection-moldedpart.

However, the above-described conventional method for producing two-colorinjection-molded parts has problems in that, since the cycle time isincreased since the process of moving back the second mold block 4 andthe first and second injection processes are performed step by step witha time difference, the manufacturing time and cost are increased.

Moreover, since the second injection process is performed after thefirstly injected molding material is solidified, the adhesion strengthbetween the first and second molding materials is reduced.

The information disclosed in this Background of the Invention section isonly for enhancement of understanding of the general background of theinvention and should not be taken as an acknowledgement or any form ofsuggestion that this information forms the prior art already known to aperson skilled in the art.

BRIEF SUMMARY OF THE INVENTION

The present invention has been made in an effort to solve theabove-described problems associated with prior art. Accordingly, variousaspects of the present invention provide for a mold and a method forproducing two-color injection-molded parts, in which different moldingmaterials are simultaneously injected to reduce injection time and apressure difference between the molding materials is induced so that oneof the molding materials is infiltrated into and bonded to anunsolidified portion of the other molding material duringsolidification.

One aspect of the present invention is directed to a mold for producingtwo-color injection-molded parts, the mold including a first mold blockand a second mold block, which may be arranged side-by-side, a dieincluding a first cavity and a second cavity disposed between the dieand the first and second mold blocks, respectively, a slide moldprovided between the first and second mold blocks and being configuredto contract when a pressure within at least one of the first and secondcavities rises above a predetermined level, and/or a first gate and asecond gate provided in the first cavity and the second cavity to guidea first molding material and a second molding material simultaneouslyinjected from an injector to the first cavity and the second cavity,respectively.

The slide mold may include a reciprocator biasing an upper block awayfrom a lower block towards the first and second cavities.

The slide mold may be configured to interconnect the first cavity andthe second cavity when the pressure rises above the predetermined leveland moves the upper block towards the lower block.

A first distance between the first gate and the slide mold may be lessthan a second distance between the second gate and the slide mold.

The slide mold may include a reciprocator biasing an upper block awayfrom a lower block towards the first and second cavities.

The slide mold may be configured to interconnect the first cavity andthe second cavity when the pressure rises above the predetermined leveland moves the upper block towards the lower block.

Another aspect of the present invention is directed to a method forproducing two-color injection-molded parts, the method includingsimultaneously injecting a first material and a second material into adie through a first gate and a second gate, respectively, to fill afirst cavity and a second cavity respectively defined by the die and afirst mold block and a second mold block, closing the second gate,and/or pressurizing the first gate such that the first molding material,while unsolidified, pushes a slide mold provided between the first andsecond mold blocks thereby allowing the first molding material toinfiltrated into an unsolidified layer of the second molding material.

The slide mold may include a reciprocator biasing an upper block awayfrom a lower block towards the first and second cavities.

The slide mold may be configured to interconnect the first cavity andthe second cavity when the pressure rises above the predetermined leveland moves the upper block towards the lower block, the method mayinclude bonding the first molding material may be to the second moldingmaterial.

A first distance between the first gate and the slide mold may be lessthan a second distance between the second gate and the slide mold.

The slide mold may include a reciprocator biasing an upper block awayfrom a lower block towards the first and second cavities.

The slide mold may be configured to interconnect the first cavity andthe second cavity when the pressure rises above the predetermined leveland moves the upper block towards the lower block, the method mayinclude bonding the first molding material may be to the second moldingmaterial.

The method may include forming an vehicle component including the firstand second materials. The forming step may include forming a vehicledoor panel including the first and second materials.

It is understood that the term “vehicle” or “vehicular” or other similarterm as used herein is inclusive of motor vehicles in general such aspassenger automobiles including sports utility vehicles (SUV), buses,trucks, various commercial vehicles, watercraft including a variety ofboats and ships, aircraft, and the like.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description of the Invention, which togetherserve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically showing a conventional process forproducing two-color injection-molded parts.

FIG. 2 is a diagram schematically showing an exemplary molding processusing a mold for producing two-color injection-molded parts inaccordance with the present invention.

FIG. 3A is a diagram showing the operation of an exemplary main part inaccordance with the present invention.

FIGS. 3B and 3C are diagrams showing the operation of another exemplarymain part in accordance with the present invention.

FIG. 4 is an image showing a cross-section of an exemplary two-colorinjection molded part formed of different molding materials in which oneof the different molding materials is infiltrated into and bonded to theother molding materials by a pressure difference occurring therebetween.

FIG. 5 is a diagram showing an exemplary vehicle portion produced by amethod for producing two-color injection-molded parts in accordance withthe present invention.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variouspreferred features illustrative of the basic principles of theinvention. The specific design features of the present invention asdisclosed herein, including, for example, specific dimensions,orientations, locations, and shapes will be determined in part by theparticular intended application and use environment.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the invention(s) willbe described in conjunction with exemplary embodiments, it will beunderstood that present description is not intended to limit theinvention(s) to those exemplary embodiments. On the contrary, theinvention(s) is/are intended to cover not only the exemplaryembodiments, but also various alternatives, modifications, equivalentsand other embodiments, which may be included within the spirit and scopeof the invention as defined by the appended claims.

FIG. 2 is a diagram schematically showing a molding process using a moldfor producing two-color injection-molded parts in accordance with thepresent invention, FIG. 3A is a diagram showing the operation of a mainpart in accordance with various embodiments of the present invention,FIGS. 3B and 3C are diagrams showing the operation of a main part inaccordance with other embodiments of the present invention, and FIG. 4is an image showing a cross-section of a two-color injection molded partformed of different molding materials in which one of the differentmolding materials is infiltrated into and bonded to the other moldingmaterials by a pressure difference occurring therebetween.

The method for producing two-color injection-molded parts in accordancewith the present invention produces the two-color injection-molded partsby maintaining a holding pressure only in a first molding material 18such that the first molding material 18 is infiltrated into anunsolidified central core portion of a second molding material 19.

For this purpose, as shown in FIG. 2, the mold for producing two-colorinjection-molded parts in accordance with the present invention includesa die 10 disposed opposite to first and second mold blocks 11 and 12arranged side by side thus defining first and second cavities 14 and 15,in which molding materials are filled, disposed between the die 10 andthe first and second mold blocks 11 and 12. Moreover, a slide mold 20,which is moved by pressure, is provided between the first and secondmold blocks 11 and 12, and first and second gates 16 and 17, which guidethe first and second molding materials 18 and 19 injected by an injector30 to the first and second cavities 14 and 15, respectively.

At this time, the first and second molding materials 18 and 19 injectedfrom the injector 30, respectively, are formed of different resins. Theslide mold 20 has a structure in which a reciprocator such as a spring23 is disposed between an upper block 21 and a lower block 22 so as tobe contracted and moved when a pressure above a predetermined level (anelastic force of the spring) is applied as shown in FIG. 3A. Forexample, as pressure within one or both cavities rises above apredetermined level (e.g., n psi), the pressure overcomes the biasingforce of spring 23 to move upper block 21 towards lower block 22 and toa contracted position leaving slide mold in a contracted state.

Moreover, the distance between the first gate 16 and the slide mold 20is set to be smaller than that between the second gate 17 and slide mold20 so that the second molding material 19 filled in the second cavity 15is solidified more slowly than the first molding material 18 filled inthe first cavity 14.

Meanwhile, as shown in FIG. 3C, the slide mold 20 may have a structurein which the upper block 21 is formed to extend toward the second cavity15 so as to increase the bonding area between the first and secondmolding materials 18 and 19. Otherwise, as shown in FIG. 3B, the spring23 may be replaced with a hydraulic cylinder 25. In addition to, orinstead of springs and hydraulic cylinders, one will appreciate thatother suitable reciprocating means may be utilized to bias the upperblock away from the lower block and towards the first and secondcylinders.

In the case where the slide mold 20 is configured by replacing thespring 23 with the hydraulic cylinder 25, the slide mold 20 iscontracted and moved by the operation of the hydraulic cylinder 25, andthereby the slide mold 20 can be moved regardless of the magnitude ofthe holding pressure in the first gate 16 or moved forcibly.

Next, the method for producing two-color injection-molded parts usingthe above-described mold in accordance with the present invention willbe described.

According to the present invention, the first and second moldingmaterials 18 and 19 are simultaneously injected from the injector 30 andsimultaneously filled in the first and second cavities 14 and 15 throughthe first and second gates 16 and 17.

When the molding materials are filled in the above manner, a holdingpressure is maintained until the molding materials do not flow backwardas the gates are solidified so that the molding materials flow backwardand the contraction amount is supplemented. At this time, the first gate16 is kept open so as to maintain a constant pressure until the moldingmaterial is solidified, and the second gate 17 is closed to cut off theholding pressure.

As shown in FIGS. 3A and 3B, the molding materials 18 and 19 filled inthe first and second cavities 14 and 15 are solidified from the outsidewhich is in contact with the wall surface of the mold toward the insidegradually. The first molding material 18 pushes the upper block 21 ofthe slide mold 20 due to the holding pressure of the first gate 16 andis filled in an empty space.

The first molding material 18, which is not unsolidified, is infiltratedinto an unsolidified portion (or unsolidified layer) of the secondmolding material 19 by a pressure difference due to the holding pressureand bonded to the second molding material 19 and solidified.

Moreover, a difference between the distances from the first and secondgates 16 and 17 to the slide mold 20 is set to be relatively large(d1<<d2), and thereby the solidification rate of the second moldingmaterial 19 is lower than that of the first molding material 18 suchthat the first molding material 18 is infiltrated into the unsolidifiedlayer of the second molding material 19.

The first molding material 18 infiltrated into the unsolidified layer ofthe second molding material 19 is solidified and subjected to a coolingprocess, thus obtaining the two-color injection-molded part.

Meanwhile, as shown in FIG. 3C, in the case where the upper block 21 ofthe slide mold 20 is formed to extend, the area where the first moldingmaterial 18 is bonded to the second material 19 is increased, andthereby the bonding strength is increased.

In other words, according to the present invention, since the first andsecond molding materials 18 and 19 are simultaneously injected from theinjector 30 and simultaneously filled in the first and second cavities14 and 15, the injection time is reduced to approximately 30% comparedwith the conventional method. Moreover, since one of the moldingmaterials is infiltrated into the other molding material, the materialsare bonded to each other during solidification, and thereby the bondingstrength is increased.

As described above, the present invention may have the followingeffects.

Since one of the different molding materials is infiltrated into theother molding material and solidified during the injection moldingprocess, the bonding strength is increased. Moreover, since thedifferent molding materials are simultaneously injected and filled, theinjection time is reduced.

Furthermore, the manufacturing time is reduced due to the reduction inthe injection time, and thereby the manufacturing cost is reduced.

For convenience in explanation and accurate definition in the appendedclaims, the terms “upper” or “lower”, “inside”, and etc. are used todescribe features of the exemplary embodiments with reference to thepositions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The exemplary embodiments were chosen and described in orderto explain certain principles of the invention and their practicalapplication, to thereby enable others skilled in the art to make andutilize various exemplary embodiments of the present invention, as wellas various alternatives and modifications thereof It is intended thatthe scope of the invention be defined by the Claims appended hereto andtheir equivalents.

1. A method for producing two-color injection-molded parts, the methodcomprising: simultaneously injecting a first material and a secondmaterial into a die through a first gate and a second gate,respectively, to fill a first cavity and a second cavity respectivelydefined by the die and a first mold block and a second mold block;closing the second gate; and pressurizing the first gate such that thefirst molding material, while unsolidified, pushes a slide mold providedbetween the first and second mold blocks, thereby allowing the firstmolding material to be infiltrated into an unsolidified layer of thesecond molding material by a restoring force of the slide mold.
 2. Themethod of claim 1, wherein the slide mold includes a reciprocatorbiasing an upper block away from a lower block towards the first andsecond cavities.
 3. The method of claim 2, wherein the slide mold isconfigured to interconnect the first cavity and the second cavity whensaid pressure rises above said predetermined level and moves the upperblock towards the lower block, said method further comprising bondingthe first molding material is to the second molding material.
 4. Themethod of claim 1, wherein a first distance between the first gate andthe slide mold is less than a second distance between the second gateand the slide mold.
 5. The method of claim 4, wherein the slide moldincludes a reciprocator biasing an upper block away from a lower blocktowards the first and second cavities.
 6. The method of claim 5, whereinthe slide mold is configured to interconnect the first cavity and thesecond cavity when said pressure rises above said predetermined leveland moves the upper block towards the lower block, said method furthercomprising bonding the first molding material is to the second moldingmaterial.
 7. The method of claim 1, further comprising: forming avehicle component including said first and second materials.
 8. Themethod of claim 7, wherein said forming step comprises: forming avehicle door panel including said first and second materials.